Poly(β-amino ester)-co-poly(caprolactone) Terpolymers as Nonviral Vectors for mRNA Delivery In Vitro and In Vivo

Leveraging high-throughput screening technologies in targeted mRNA delivery

Messenger ribonucleic acid (mRNA) has emerged as a promising molecular preventive and therapeutic approach that opens new avenues for healthcare. Although the use of delivery systems, especially lipid nanoparticles (LNPs), greatly improves the efficiency and stability of mRNA, mRNA tends to accumulate in the liver and hardly penetrates physiological barriers to reach the target site after intravenous injection. Hence, the rational design of targeting strategies aimed at directing mRNA to specific tissues and cells remains an enormous challenge in mRNA therapy. High-throughput screening (HTS) is a cutting-edge targeted technique capable of synthesizing chemical compound libraries for the large-scale experiments to validate the efficiency of mRNA delivery system. In this review, we firstly provide an overview of conventional low-throughput targeting strategies. Then the latest advancements in HTS techniques for mRNA targeted delivery, encompassing optimizing structures of large-scale delivery vehicles and developing large-scale surface ligands, as well as the applications of HTS techniques in extrahepatic systemic diseases are comprehensively summarized. Moreover, we illustrate the selection of administration routes for targeted mRNA delivery. Finally, challenges in the field and potential solutions to tackle them are proposed, offering insights for future development toward mRNA targeted therapy.

From structural design to delivery: mRNA therapeutics for cancer immunotherapy

mRNA therapeutics have emerged as powerful tools for cancer immunotherapy in accordance with their superiority in expressing all sequence-known proteins in vivo. In particular, with a small dosage of delivered mRNA, antigen-presenting cells (APCs) can synthesize mutant neo-antigens and multi-antigens and present epitopes to T lymphocytes to elicit antitumor effects. In addition, expressing receptors like chimeric antigen receptor (CAR), T-cell receptor (TCR), CD134, and immune-modulating factors including cytokines, interferons, and antibodies in specific cells can enhance immunological response against tumors. With the maturation of in vitro transcription (IVT) technology, large-scale and pure mRNA encoding specific proteins can be synthesized quickly. However, the clinical translation of mRNA-based anticancer strategies is restricted by delivering mRNA into target organs or cells and the inadequate endosomal escape efficiency of mRNA. Recently, there have been some advances in mRNA-based cancer immunotherapy, which can be roughly classified as modifications of the mRNA structure and the development of delivery systems, especially the lipid nanoparticle platforms. In this review, the latest strategies for overcoming the limitations of mRNA-based cancer immunotherapies and the recent advances in delivering mRNA into specific organs and cells are summarized. Challenges and opportunities for clinical applications of mRNA-based cancer immunotherapy are also discussed.

mRNA Delivery: Challenges and Advances through Polymeric Soft Nanoparticles

Single-stranded messenger ribonucleic acid (mRNA) plays a pivotal role in transferring genetic information, and tremendous effort has been devoted over the years to utilize its transcription efficacy in therapeutic interventions for a variety of diseases with high morbidity and mortality. Lipid nanocarriers have been extensively investigated for mRNA delivery and enabled the rapid and successful development of mRNA vaccines against SARS-CoV-2. Some constraints of lipid nanocarriers have encouraged the development of alternative delivery systems, such as polymer-based soft nanoparticles, which offer a modular gene delivery platform. Such macromolecule-based nanocarriers can be synthetically articulated for tailored parameters including mRNA protection, loading efficacy, and targeted release. In this review, we highlight recent advances in the development of polymeric architectures for mRNA delivery, their limitations, and the challenges that still exist, with the aim of expediting further research and the clinical translation of such formulations.

Optimized biomimetic minerals maintain activity of mRNA complexes after long term storage

mRNA therapeutics can be readily designed, manufactured, and brought to scale, as demonstrated by widespread global vaccination against COVID-19. However, mRNA therapies require cold chain shipment and storage from manufacturing to administration, which may limit them to affluent communities. This problem could be addressed by mimicking the known ability of mineralized fossils to durably stabilize nucleic acids under extreme conditions. We synthesized and screened 40 calcium-phosphate minerals for their ability to store and maintain the activity of lyophilized mRNA complexes. The optimal mineral formulation incorporated mRNA complexes with high efficiency (77 %), and increased mRNA transfection efficiency by 5.6-fold. Lyophilized mRNA complexes stored with the optimized mineral formulation for 6 months at 25 °C were 3.2-fold more active than those stored with state-of-the-art excipients, but without a mineral. mRNA complexes stored with minerals at room temperature did not decline in transfection efficacy from 3 days to 6 months of storage, indicating that minerals can durably maintain activity of therapeutic mRNA complexes without cold chain storage. STATEMENT OF SIGNIFICANCE: Therapeutic mRNA, such as mRNA COVID-19 vaccines, require extensive cold chain storage that limits their general application. This work screened a library of minerals to maintain the activity of mRNA complexes with freeze-drying. The optimized mineral was able to maintain mRNA activity up to 6 months of storage at room temperature outperforming current methods of freeze-drying therapeutic mRNA complexes.

Building a Better Silver Bullet: Current Status and Perspectives of Non-Viral Vectors for mRNA Vaccines

In recent years, messenger RNA (mRNA) vaccines have exhibited great potential to replace conventional vaccines owing to their low risk of insertional mutagenesis, safety and efficacy, rapid and scalable production, and low-cost manufacturing. With the great achievements of chemical modification and sequence optimization methods of mRNA, the key to the success of mRNA vaccines is strictly dependent on safe and efficient gene vectors. Among various delivery platforms, non-viral mRNA vectors could represent perfect choices for future clinical translation regarding their safety, sufficient packaging capability, low immunogenicity, and versatility. In this review, the recent progress in the development of non-viral mRNA vectors is focused on. Various organic vectors including lipid nanoparticles (LNPs), polymers, peptides, and exosomes for efficient mRNA delivery are presented and summarized. Furthermore, the latest advances in clinical trials of mRNA vaccines are described. Finally, the current challenges and future possibilities for the clinical translation of these promising mRNA vectors are also discussed.

Tumor Cell Lysate-Based Multifunctional Nanoparticles Facilitate Enhanced mRNA Delivery and Immune Stimulation for Melanoma Gene Therapy

Messenger ribonucleic acid (mRNA)-based gene therapy has great potential for cancer gene therapy. However, the effectiveness of mRNA in cancer therapy needs to be further improved, and the delivery efficiency and instability of mRNA limit the application of mRNA-based products. Both the delivery efficiency can be elevated by cell-penetrating peptide modification, and the immune response can be enhanced by tumor cell lysate stimulation, representing an advantageous strategy to expand the effectiveness of mRNA gene therapy. Therefore, it is vital to exploit a vector that can deliver high-efficiency mRNA with codelivery of tumor cell lysate to induce specific immune responses. We previously reported that DMP cationic nanoparticles, formed by the self-assembly of DOTAP and mPEG-PCL, can deliver different types of nucleic acids. DMP has been successfully applied in gene therapy research for various tumor types. Here, we encapsulated tumor cell lysates with DMP nanoparticles and then modified them with a fused cell-penetrating peptide (TAT-iRGD) to form an MLSV system. The MLSV system was loaded with encoded Bim mRNA, forming the MLSV/Bim complex. The average size of the synthesized MLSV was 191.4 nm, with a potential of 47.8 mV. The MLSV/mRNA complex promotes mRNA absorption through caveolin-mediated endocytosis, with a transfection rate of up to 68.6% in B16 cells. The MLSV system could also induce the maturation and activation of dendritic cells, obviously promoting the expression of CD80, CD86, and MHC-II both in vitro and in vivo. By loading the encoding Bim mRNA, the MLSV/Bim complex can inhibit cell proliferation and tumor growth, with inhibition rates of up to 87.3% in vitro. Similarly, the MLSV/Bim complex can inhibit tumor growth in vivo, with inhibition rates of up to 78.7% in the B16 subcutaneous tumor model and 63.3% in the B16 pulmonary metastatic tumor model. Our results suggest that the MLSV system is an advanced candidate for mRNA-based immunogene therapy.

Efficient Colon Cancer Immunogene Therapy Through Co-Delivery of IL-22BP mRNA and Tumor Cell Lysate by CLSV Nanoparticles

Background

Messenger ribonucleic acid (mRNA)-based gene therapy has great potential in cancer treatment. However, the application of mRNA-based cancer treatment could be further developed. Elevated delivery ability and enhanced immune response are advantages for expanding the application of mRNA-based cancer therapy. It is crucial that the prepared carrier can cause an immune reaction based on the efficient delivery of mRNA.

Methods

We reported DMP nanoparticle previously, which was obtained by the self-assembly of 1,2-dioleoyl-3-trimethylammonium propane (DOTAP) and (ethylene glycol)-b-poly (ε-caprolactone) (mPEG-PCL). Research demonstrated that DMP can deliver mRNA, siRNA, and plasmid. And it is applied to various tumor types. In our work, the tumor cell lysate was introduced to the internal DMP chain, fusing cell-penetrating peptides (CPPs) modification on the surface forming the CLSV system. And then mixed encoded IL-22BP (interleukin-22 binding protein) mRNA and CLSV to form CLSV/IL-22BP complex.

Results

The size of the CLSV system was 213.2 nm, and the potential was 45.7 mV. The transfection efficiency of the CLSV system is up to 76.45% in C26 cells via the micropinocytosis pathway. The CLSV system also could induce an immune response and significantly elevate the expression of CD80, CD86, and MHC-II in vivo. Then, by binding with IL-22BP (Interleukin-22 binding protein) mRNA, the CLSV/IL-22BP complex inhibited tumor cell growth, with an inhibition rate of up to 82.3% in vitro. The CLSV/IL-22BP complex also inhibited tumor growth in vivo, the tumor cell growth inhibition up to 75.0% in the subcutaneous tumor model, and 84.9% in the abdominal cavity metastasis tumor model.

Conclusion

Our work demonstrates that the CLSV system represents a potent potential for mRNA delivery.

Delivery of nucleic acids using nanomaterials

The increasing number of approved nucleic acid therapeutics demonstrates the potential for the prevention and treatment of a broad spectrum of diseases. This trend underscores the significant impact and promise of nucleic acid-based treatments in the field of medicine. Nevertheless, employing nucleic acids as therapeutics is challenging due to their susceptibility to degradation by nucleases and their unfavorable physicochemical characteristics that hinder delivery into cells. Appropriate vectors play a pivotal role in improving nucleic acid stability and delivering nucleic acids into specific cells. The maturation of delivery systems has led to breakthroughs in the development of therapeutics based on nucleic acids such as DNA, siRNA, and mRNA. Non-viral vectors have gained prominence among the myriad of nanomaterials due to low immunogenicity, ease of manufacturing, and simplicity of cost-effective, large-scale production. Here, we provide an overview of the recent advancements in nanomaterials for nucleic acid delivery. Specifically, we give a detailed introduction to the characteristics of polymers, lipids, and polymer-lipid hybrids, and provide comprehensive descriptions of their applications in nucleic acid delivery. Also, biological barriers, administration routes, and strategies for organ-selective delivery of nucleic acids are discussed. In summary, this review offers insights into the rational design of next-generation delivery vectors for nucleic acid delivery.

Cellular Trafficking of Nanotechnology-Mediated mRNA Delivery

Messenger RNA (mRNA)-based therapy has emerged as a powerful, safe, and rapidly scalable therapeutic approach that involves technologies for both mRNA itself and the delivery vehicle. Although there are some unique challenges for different applications of mRNA therapy, a common challenge for all mRNA therapeutics is the transport of mRNA into the target cell cytoplasm for sufficient protein expression. This review is focused on the behaviors at the cellular level of nanotechnology-mediated mRNA delivery systems, which have not been comprehensively reviewed yet. First, the four main therapeutic applications of mRNA are introduced, including immunotherapy, protein replacement therapy, genome editing, and cellular reprogramming. Second, common types of mRNA cargos and mRNA delivery systems are summarized. Third, strategies to enhance mRNA delivery efficiency during the cellular trafficking process are highlighted, including accumulation to the cell, internalization into the cell, endosomal escape, release of mRNA from the nanocarrier, and translation of mRNA into protein. Finally, the challenges and opportunities for the development of nanotechnology-mediated mRNA delivery systems are presented. This review can provide new insights into the future fabrication of mRNA nanocarriers with desirable cellular trafficking performance.

Elucidating the Effect of Amine Charge State on Poly(β-amino ester) Degradation Using Permanently Charged Analogs

With synthetic ease and tunable degradation lifetimes, poly(β-amino ester)s (PBAEs) have found use in increasingly diverse applications, from gene therapy to thermosets. Protonatable amines in each repeating unit impart pH-dependent solution behavior and lifetimes, with acidic conditions favoring solubility, yet slowing hydrolysis. Due in part to these interconnected phenomena governing pH-dependent PBAE degradation, predictive degradation models, which would enable user-defined lifetimes, remain elusive. To separate the effects of charge state and solution pH on PBAE degradation, we synthesized poly(β-quaternary ammonium ester)s (PBQAEs), which differ from their parent PBAEs only by an additional methyl group, generating polymers with pH-independent cationic charge. Like PBAEs, PBQAE hydrolysis accelerates with increasing pH, although at a given pH, PBAE degradation outpaces PBQAE degradation. This difference is more pronounced in basic solutions, suggesting that deprotonated PBAE amines accelerate hydrolysis, providing an additional tuning parameter to PBAE lifetime and informing the degradation of PBAEs and other pH-responsive polymers.

mRNA nanodelivery systems: targeting strategies and administration routes

With the great success of coronavirus disease (COVID-19) messenger ribonucleic acid (mRNA) vaccines, mRNA therapeutics have gained significant momentum for the prevention and treatment of various refractory diseases. To function efficiently in vivo and overcome clinical limitations, mRNA demands safe and stable vectors and a reasonable administration route, bypassing multiple biological barriers and achieving organ-specific targeted delivery of mRNA. Nanoparticle (NP)-based delivery systems representing leading vector approaches ensure the successful intracellular delivery of mRNA to the target organ. In this review, chemical modifications of mRNA and various types of advanced mRNA NPs, including lipid NPs and polymers are summarized. The importance of passive targeting, especially endogenous targeting, and active targeting in mRNA nano-delivery is emphasized, and different cellular endocytic mechanisms are discussed. Most importantly, based on the above content and the physiological structure characteristics of various organs in vivo, the design strategies of mRNA NPs targeting different organs and cells are classified and discussed. Furthermore, the influence of administration routes on targeting design is highlighted. Finally, an outlook on the remaining challenges and future development toward mRNA targeted therapies and precision medicine is provided.

mRNA-Based Nanomedicine: A New Strategy for Treating Infectious Diseases and Beyond

Messenger RNA (mRNA) has emerged as a new therapeutic agent for the prevention and treatment of a wide range of diseases. The recent achievement of the two lipid nanoparticle-mRNA vaccines developed by Moderna and Pfizer-BioNTech against coronavirus 2019 (COVID-19) disease in record time highlights the huge potential of mRNA technology and reshaping the landscape of vaccine development and the future of gene therapies. Challenges related to translational efficacy, mRNA stability, immunogenicity, and ensuring the quality of final products have been significantly improved by recent advancements in mRNA engineering and delivery. Thus, the present review aims to provide the latest innovations that incrementally overcome these issues and future directions in the context of ongoing clinical trials against infectious diseases and beyond.

Polymer-Based mRNA Delivery Strategies for Advanced Therapies

Messenger RNA (mRNA)-based therapies offer great promise for the treatment of a variety of diseases. In 2020, two FDA approvals of mRNA-based vaccines have elevated mRNA vaccines to global recognition. However, the therapeutic capabilities of mRNA extend far beyond vaccines against infectious diseases. They hold potential for cancer vaccines, protein replacement therapies, gene editing therapies, and immunotherapies. For realizing such advanced therapies, it is crucial to develop effective carrier systems. Recent advances in materials science have led to the development of promising nonviral mRNA delivery systems. In comparison to other carriers like lipid nanoparticles, polymer-based delivery systems often receive less attention, despite their unique ability to carefully tune their chemical features to promote mRNA protection, their favorable pharmacokinetics, and their potential for targeting delivery. In this review, the central features of polymer-based systems for mRNA delivery highlighting the molecular design criteria, stability, and biodistribution are discussed. Finally, the role of targeting ligands for the future of RNA therapies is analyzed.

A Polymeric Nanoparticle Formulation for Targeted mRNA Delivery to Fibroblasts

Messenger RNA (mRNA)-based therapies offer enhanced control over the production of therapeutic proteins for many diseases. Their clinical implementation warrants formulations capable of delivering them safely and effectively to target sites. Owing to their chemical versatility, polymeric nanoparticles can be designed by combinatorial synthesis of different ionizable, cationic, and aromatic moieties to modulate cell targeting, using inexpensive formulation steps. Herein, 152 formulations are evaluated by high-throughput screening using a reporter fibroblast model sensitive to functional delivery of mRNA encoding Cre recombinase. Using in vitro and in vivo models, a polymeric nanoformulation based on the combination of 3 specific monomers is identified to transfect fibroblasts much more effectively than other cell types populating the skin, with superior performance than lipid-based transfection agents in the delivery of Cas9 mRNA and guide RNA. This tropism can be explained by receptor-mediated endocytosis, involving CD26 and FAP, which are overexpressed in profibrotic fibroblasts. Structure-activity analysis reveals that efficient mRNA delivery required the combination of high buffering capacity and low mRNA binding affinity for rapid release upon endosomal escape. These results highlight the use of high-throughput screening to rapidly identify chemical features towards the design of highly efficient mRNA delivery systems targeting fibrotic diseases.

Net anionic poly(β-amino ester)s: synthesis, pH-dependent behavior, and complexation with cationic cargo

As hydrolytically-labile, traditionally-cationic polymers, poly(β-amino ester)s (PBAEs) adeptly complex anionic compounds such as nucleic acids, and release their cargo as the polymer degrades. To engineer fully-degradable polyelectrolyte complexes and delivery vehicles for cationic therapeutics, we sought to invert PBAE net charge to generate net anionic PBAEs. Since PBAEs can carry up to a net charge of +1 per tertiary amine, we synthesized a series of alkyne-functionalized PBAEs that allowed installation of 2 anionic thiol-containing molecules per tertiary amine via a radical thiol-yne reaction. Finding dialysis in aqueous solution to lead to PBAE degradation, we developed a preparative size exclusion chromatography method to remove unreacted thiol from the net anionic PBAEs without triggering hydrolysis. The net anionic PBAEs display non-monotonic solution behavior as a function of pH, being more soluble at pH 4 and 10 than in intermediate pH ranges. Like cationic PBAEs, these net anionic PBAEs degrade in aqueous environments with hydrophobic content-dependent hydrolysis, as determined by 1H NMR spectroscopy. Further, these net anionic PBAEs form complexes with the cationic peptide (GR)10, which disintegrate over time as the polymer hydrolyzes. Together, these studies outline a synthesis and purification route to make previously inaccessible net anionic PBAEs with tunable solution and degradation behavior, allowing for user-determined complexation and release rates and providing opportunities for degradable polyelectrolyte complexes and cationic therapeutic delivery.

Enhanced Immune Responses to Mucosa by Functionalized Chitosan-Based Composite Nanoparticles as a Vaccine Adjuvant for Intranasal Delivery

Nasal administration for vaccine delivery is a novel non-invasive vaccine administration approach that can induce local or systemic immune responses and overcome the disadvantages caused by traditional injectable administration. However, mucosal vaccine and adjuvant delivery systems with sustained-release ability and enhanced immune effects at mucosal sites have still been highly demanded. In this work, N-2-hydroxypropyl trimethyl ammonium chloride chitosan/N,O-carboxymethyl chitosan nanoparticles (N-2-HACC/CMCS NPs) with excellent mucosal absorption, high drug loading capacity, and enhanced immune responses were prepared by the ionic cross-linking method. To evaluate the potential capacity of the N-2-HACC/CMCS NPs as a vaccine adjuvant and the molecular mechanism for the induction of enhanced mucosal and systemic immune responses, bovine serum albumin (BSA) was employed as a general model antigen and loaded into the N-2-HACC/CMCS NPs to prepare a BSA-loaded N-2-HACC/CMCS adjuvant vaccine (N-2-HACC/CMCS/BSA NPs). It was well demonstrated that the N-2-HACC/CMCS/BSA NPs with great biostability and mucosal absorption could effectively promote the proliferation of lymphocytes and the secretion of related pro-inflammatory factors, resulting in the stimulation of specific mucosal and systemic immune responses. This study revealed that the chitosan-based nano-delivery system can act as the mucosal vaccine adjuvant and possesses great promise in viral infectious diseases and immunization therapy.

Helper-Polymer Based Five-Element Nanoparticles (FNPs) for Lung-Specific mRNA Delivery with Long-Term Stability after Lyophilization

Lipid nanoparticles (LNPs) carrying therapeutic mRNAs hold great promise in treating lung-associated diseases like viral infections, tumors, and genetic disorders. However, because of their thermodynamically unstable nature, traditional LNPs carrying mRNAs need to be stored at low temperatures, which hinders their prevalence. Herein, an efficient lung-specific mRNA delivery platform named five-element nanoparticles (FNPs) is developed in which helper-polymer poly(β-amino esters) (PBAEs) and DOTAP are used in combination. The new strategy endows FNPs with high stability by increasing the charge repulsion between nanoparticles and the binding force of the aliphatic chains within the nanoparticles. The structure-activity relationship (SAR) shows that PBAEs with E1 end-caps, higher degrees of polymerization, and longer alkyl side chains exhibit higher hit rates. Lyophilized FNP formulations can be stably stored at 4 °C for at least 6 months. Overall, a novel delivery platform with high efficiency, specificity, and stability was developed for advancing mRNA-based therapies for lung-associated diseases.

Feasibility and application of machine learning enabled fast screening of poly-beta-amino-esters for cartilage therapies

Despite the large prevalence of diseases affecting cartilage (e.g. knee osteoarthritis affecting 16% of population globally), no curative treatments are available because of the limited capacity of drugs to localise in such tissue caused by low vascularisation and electrostatic repulsion. While an effective delivery system is sought, the only option is using high drug doses that can lead to systemic side effects. We introduced poly-beta-amino-esters (PBAEs) to effectively deliver drugs into cartilage tissues. PBAEs are copolymer of amines and di-acrylates further end-capped with other amine; therefore encompassing a very large research space for the identification of optimal candidates. In order to accelerate the screening of all possible PBAEs, the results of a small pool of polymers (n = 90) were used to train a variety of machine learning (ML) methods using only polymers properties available in public libraries or estimated from the chemical structure. Bagged multivariate adaptive regression splines (MARS) returned the best predictive performance and was used on the remaining (n = 3915) possible PBAEs resulting in the recognition of pivotal features; a further round of screening was carried out on PBAEs (n = 150) with small variations of structure of the main candidates from the first round. The refinements of such characteristics enabled the identification of a leading candidate predicted to improve drug uptake > 20 folds over conventional clinical treatment; this uptake improvement was also experimentally confirmed. This work highlights the potential of ML to accelerate biomaterials development by efficiently extracting information from a limited experimental dataset thus allowing patients to benefit earlier from a new technology and at a lower price. Such roadmap could also be applied for other drug/materials development where optimisation would normally be approached through combinatorial chemistry.

mRNA-based modalities for infectious disease management

The novel coronavirus disease 2019 (COVID-19) is still rampant all over the world, causing incalculable losses to the world. Major pharmaceutical organizations around the globe are focusing on vaccine research and drug development to prevent further damage caused by the pandemic. The messenger RNA (mRNA) technology has got ample of attention after the success of the two very effective mRNA vaccines during the recent pandemic of COVID-19. mRNA vaccine has been promoted to the core stage of pharmaceutical industry, and the rapid development of mRNA technology has exceeded expectations. Beyond COVID-19, the mRNA vaccine has been tested for various infectious diseases and undergoing clinical trials. Due to the ability of constant mutation, the viral infections demand abrupt responses and immediate production, and therefore mRNA-based technology offers best answers to sudden outbreaks. The need for mRNA-based vaccine became more obvious due to the recent emergence of new Omicron variant. In this review, we summarized the unique properties of mRNA-based vaccines for infectious diseases, delivery technologies, discussed current challenges, and highlighted the prospects of this promising technology in the future. We also discussed various clinical studies as well preclinical studies conducted on mRNA therapeutics for diverse infectious diseases.

Emerging mRNA technologies: delivery strategies and biomedical applications

The great success achieved by the two highly-effective messenger RNA (mRNA) vaccines during the COVID-19 pandemic highlights the great potential of mRNA technology. Through the evolution of mRNA technology, chemistry has played an important role from mRNA modification to the synthesis of mRNA delivery platforms, which allows various applications of mRNA to be achieved both in vitro and in vivo. In this tutorial review, we provide a summary and discussion on the significant progress of emerging mRNA technologies, as well as the underlying chemical designs and principles. Various nanoparticle (NP)-based delivery strategies including protein-mRNA complex, lipid-based carriers, polymer-based carriers, and hybrid carriers for the efficient delivery of mRNA molecules are presented. Furthermore, typical mRNA delivery platforms for various biomedical applications (e.g., functional protein expression, vaccines, cancer immunotherapy, and genome editing) are highlighted. Finally, our insights into the challenges and future development towards clinical translation of these mRNA technologies are provided.

Poly (β amino esters) copolymers: Novel potential vectors for delivery of genes and related therapeutics

The unique properties of polymers have performed an essential contribution to the drug delivery system by providing an outstanding platform for the delivery of macromolecules and genes. However, the block copolymers have been the subject of many recently published works whose results have demonstrated excellent performance in drug targeting. Poly(β-amino esters) (PβAEs) copolymers are the synthetic cationic polymers that are tailored by chemically joining PβAEs with other additives to demonstrate extraordinary efficiency in designing pre-defined and pre-programmed nanostructures, site-specific delivery, andovercoming the distinct cellular barriers. Different compositional and structural libraries could be generated by combinatorial chemistry and by the addition of various novel functional additives that fulfill the multiple requirements of targeted delivery. These intriguing attributes allow PβAE-copolymers to have customized therapeutic functions such as excellent encapsulation capacity, high stability, and stimuli-responsive release. Here, we give an overview of PβAE copolymers-based formulations along with focusing on most notable improvements such as structural modifications, bio-conjugations, and stimuli-responsive approaches, for safe and effective nucleic acids delivery.

Polymers Strive for Accuracy: From Sequence-Defined Polymers to mRNA Vaccines against COVID-19 and Polymers in Nucleic Acid Therapeutics

Unquestionably, polymers have influenced the world over the past 100 years. They are now more crucial than ever since the COVID-19 pandemic outbreak. The pandemic paved the way for certain polymers to be in the spotlight, namely sequence-defined polymers such as messenger ribonucleic acid (mRNA), which was the first type of vaccine to be authorized in the U.S. and Europe to protect against the SARS-CoV-2 virus. This rise of mRNA will probably influence scientific research concerning nucleic acids in general and RNA therapeutics in specific. In this Perspective, we highlight the recent trends in sequence-controlled and sequence-defined polymers. Then we discuss mRNA vaccines as an example to illustrate the need of ultimate sequence control to achieve complex functions such as specific activation of the immune system. We briefly present how mRNA vaccines are produced, the importance of modified nucleotides, the characteristic features, and the advantages and challenges associated with this class of vaccines. Finally, we discuss the chances and opportunities for polymer chemistry to provide solutions and contribute to the future progress of RNA-based therapeutics. We highlight two particular roles of polymers in this context. One represents conjugation of polymers to nucleic acids to form biohybrids. The other is concerned with advanced polymer-based carrier systems for nucleic acids. We believe that polymers can help to address present problems of RNA-based therapeutic technologies and impact the field beyond the COVID-19 pandemic.

Systematic Combination of Oligonucleotides and Synthetic Polymers for Advanced Therapeutic Applications

The potential of oligonucleotides is exceptional in therapeutics because of their high safety, potency, and specificity compared to conventional therapeutic agents. However, many obstacles, such as low in vivo stability and poor cellular uptake, have hampered their clinical success. Use of polymeric carriers can be an effective approach for overcoming the biological barriers and thereby maximizing the therapeutic efficacy of the oligonucleotides due to the availability of highly tunable synthesis and functional modification of various polymers. As loaded in the polymeric carriers, the therapeutic oligonucleotides, such as antisense oligonucleotides, small interfering RNAs, microRNAs, and even messenger RNAs, become nuclease-resistant by bypassing renal filtration and can be efficiently internalized into disease cells. In this review, we introduced a variety of systematic combinations between the therapeutic oligonucleotides and the synthetic polymers, including the uses of highly functionalized polymers responding to a wide range of endogenous and exogenous stimuli for spatiotemporal control of oligonucleotide release. We also presented intriguing characteristics of oligonucleotides suitable for targeted therapy and immunotherapy, which can be fully supported by versatile polymeric carriers.

High-throughput screening of nanoparticles in drug delivery

The use of pharmacologically active compounds to manage and treat diseases is of utmost relevance in clinical practice. It is well recognized that spatial-temporal control over the delivery of these biomolecules will greatly impact their pharmacokinetic profile and ultimately their therapeutic effect. Nanoparticles (NPs) prepared from different materials have been tested successfully in the clinic for the delivery of several biomolecules including non-coding RNAs (siRNA and miRNA) and mRNAs. Indeed, the recent success of mRNA vaccines is in part due to progress in the delivery systems (NP based) that have been developed for many years. In most cases, the identification of the best formulation was done by testing a small number of novel formulations or by modification of pre-existing ones. Unfortunately, this is a low throughput and time-consuming process that hinders the identification of formulations with the highest potential. Alternatively, high-throughput combinatorial design of NP libraries may allow the rapid identification of formulations with the required release and cell/tissue targeting profile for a given application. Combinatorial approaches offer several advantages over conventional methods since they allow the incorporation of multiple components with varied chemical properties into materials, such as polymers or lipid-like materials, that will subsequently form NPs by self-assembly or chemical conjugation processes. The current review highlights the impact of high-throughput in the development of more efficient drug delivery systems with enhanced targeting and release kinetics. It also describes the current challenges in this research area as well as future directions.

Synthetic modified messenger RNA for therapeutic applications

Synthetic modified messenger RNA (mRNA) has manifested great potentials for therapeutic applications such as vaccines and gene therapies, with the recent mRNA vaccines for global pandemic COVID-19 (corona virus disease 2019) attracting the tremendous attention. The chemical modifications and delivery vehicles of synthetic mRNAs are the two key factors for their in vivo therapeutic applications. Chemical modifications like nucleoside methylation endow the synthetic mRNAs with high stability and reduced stimulation of innate immunity. The development of scalable production of synthetic mRNA and efficient mRNA formulation and delivery strategies in recent years have remarkably advanced the field. It is worth noticing that we had limited knowledge on the roles of mRNA modifications in the past. However, the last decade has witnessed not only new discoveries of several naturally occurring mRNA modifications but also substantial advances in understanding their roles on regulating gene expression. It is highly necessary to reconsider the therapeutic system made by synthetic modified mRNAs and delivery vectors. In this review, we will mainly discuss the roles of various chemical modifications on synthetic mRNAs, briefly summarize the progresses of mRNA delivery strategies, and highlight some latest mRNA therapeutics applications including infectious disease vaccines, cancer immunotherapy, mRNA-based genetic reprogramming and protein replacement, mRNA-based gene editing.

Statement of significance

The development of synthetic mRNA drug holds great promise but lies behind small molecule and protein drugs largely due to the challenging issues regarding its stability, immunogenicity and potency. In the last 15 years, these issues have beensubstantially addressed by synthesizing chemically modified mRNA and developing powerful delivery systems; the mRNA therapeutics has entered an exciting new era begun with the approved mRNA vaccines for the COVID-19 infection disease. Here, we provide recent progresses in understanding the biological roles of various RNA chemical modifications, in developing mRNA delivery systems, and in advancing the emerging mRNA-based therapeutic applications, with the purpose to inspire the community to spawn new ideas for curing diseases.

Functionalized DMP-039 Hybrid Nanoparticle as a Novel mRNA Vector for Efficient Cancer Suicide Gene Therapy

Background

Gene therapy has emerged as a new strategy for cancer therapy. As an alternative nucleic acid material, messenger ribonucleic acid (mRNA) is being increasingly utilized in cancer gene therapy. However, unfulfilled requirements and a lack of ideal mRNA delivery vectors persist.

Methods

We developed an advanced mRNA delivery system, DMP-039, by fusing a cell-penetrating peptide, cRGD-R9, and a cationic nano-sized DMP backbone together. The DMP gene vector backbone was synthesized by the self-assembly of DOTAP lipid and mPEG-PCL polymer. Introduction of the cRGD-R9 peptide onto the DMP backbone was performed to elevate the mRNA delivery capacity, which resulted in a peptide-functionalized hybrid delivery system.

Results

The average size of the synthesized DMP-039 was 268.9 ± 12.4 nm (PDI = 0.382), with a potential of 17.4 ± 0.5 mV. The synthesized DMP-039 hybrid nanoparticles exhibited high mRNA delivery efficiency through multiple mechanisms during transmembrane transportation. By loading the encoding mRNA from the suicide gene Bim, a locally administered mBim/DMP-039 complex strongly inhibited growth in two colon cancer models. Moreover, intravenous administration of the mBim/DMP-039 complex efficiently suppressed C26 pulmonary metastatic tumor progression with high safety. The in vivo distribution, degradation, and excretion were also investigated in detail.

Conclusion

Our results suggest that the DMP-039 peptide-functionalized hybrid nanoparticle is an advanced candidate for mRNA-based suicide gene therapy.

Location of a single histidine within peptide carriers increases mRNA delivery

BACKGROUND

Previously, we determined that four-branched histidine-lysine (HK) peptides were effective carriers of plasmids and small interfering RNA. In the present study, we compared several branched HK carriers and, in particular, two closely-related H3K4b and H3K(+H)4b peptides for their ability as carriers of mRNA. The H3K(+H)4b peptide differed from its parent analogue, H3K4b, by only a single histidine in each branch.

METHODS

A series of four-branched HK peptides with varied sequences was synthesized on a solid-phase peptide synthesizer. The ability of these peptides to carry mRNA expressing luciferase to MDA-MB-231 cells was investigated. With gel retardation and heparin displacement assays, the stability of HK polyplexes was examined. We determined the intracellular uptake of HK polyplexes by flow cytometry and fluorescence microscopy. The size and polydispersity index of the polyplexes in several media were measured by dynamic light scattering.

RESULTS

MDA-MB-231 cells transfected by H3K(+H)4b-mRNA polyplexes expressed 10-fold greater levels of luciferase than H3K4b polyplexes. With gel retardation and heparin displacement assays, the H3K(+H)4b polyplexes showed greater stability than H3K4b. Intracellular uptake and co-localization of H3K(+H)4b polyplexes within acidic endosomes were also significantly increased compared to H3K4b. Similar to H3K(+H)4b, several HK analogues with an additional histidine in the second domain of their branches were effective carriers of mRNA. When combined with DOTAP liposomes, H3K(+H)4b was synergistic in delivery of mRNA.

CONCLUSIONS

H3K(+H)4b was a more effective carrier of mRNA than H3K4b. Mechanistic studies suggest that H3K(+H)4b polyplexes were more stable than H3K4b polyplexes. Lipopolyplexes formed with H3K(+H)4b markedly increased mRNA transfection.

mRNA technology as one of the promising platforms for the SARS-CoV-2 vaccine development

After the genome sequence of SARS-CoV-2 (Severe acute respiratory syndrome-related coronavirus 2) was published and the number of infected people began to increase rapidly, many global companies began to develop a vaccine. Almost all known approaches to vaccine design were applied for this purpose, including inactivated viruses, mRNA and DNA-vaccines, vaccines based on various viral vectors, synthetically generated peptides and recombinant proteins produced in cells of insects and mammals. This review considers one of the promising vaccine platforms based on messenger RNA. Until recent years, mRNA-vaccination was out of practical implementation due to high sensitivity to nuclease degradation and consequent instability of drugs based on mRNA. Latest technological advances significantly mitigated the problems of low immunogenicity, instability, and difficulties in RNA-vaccine delivery. It is worth noting that mRNA-vaccines can efficiently activate both components of the immune system, i. e. T-cell and humoral responses. The essential advantage of mRNAvaccines includes fast, inexpensive, scalable and uniform production providing a large output of desirable products in vitro. Synthesis and purification processes significantly simplify the process technology of mRNA drugs with injectable purity. Thus, mRNA production via in vitro transcription is more advantageous as compared with DNA-vaccines since it is a chemical process without the use of cells. mRNA techniques make it possible to pass all the phases of vaccine development much faster in comparison with the production of vaccines based on inactivated viruses or recombinant proteins. This property is critically important when designing vaccines against viral pathogens as the main problem of disease control includes a time gap between an epidemic and vaccine development. This paper discusses studies on the development of vaccines against coronaviruses including SARS-CoV-2 with special attention to the mRNA technique.

Off the beaten path: Novel mRNA-nanoformulations for therapeutic vaccination against HIV

Over the last few years, immunotherapy for HIV in general and therapeutic vaccination in particular, has received a tremendous boost, both in preclinical research and in clinical applications. This interest is based on the evidence that the immune system plays a crucial role in controlling HIV infection, as shown for long-term non-progressors and elite controllers, and that immune responses can be manipulated towards targeting conserved epitopes. So far, the most successful approach has been vaccination with autologous dendritic cells (DCs) loaded ex vivo with antigens and activation signals. Although this approach offers much promise, it also comes with significant drawbacks such as the requirement of a specialized infrastructure and expertise, as well as major challenges for logistics and storage, making it extremely time consuming and costly. Therefore, methods are being developed to avoid the use of ex vivo generated, autologous DCs. One of these methods is based on mRNA for therapeutic vaccination. mRNA has proven to be a very promising vaccine platform, as the coding information for any desired protein, including antigens and activation signals, can be generated in a very short period of time, showing promise both as an off-the-shelf therapy and as a personalized approach. However, an important drawback of this approach is the short half-life of native mRNA, due to the presence of ambient RNases. In addition, proper immunization requires that the antigens are expressed, processed and presented at the right immunological site (e.g. the lymphoid tissues). An ambivalent aspect of mRNA as a vaccine is its capacity to induce type I interferons, which can have beneficial adjuvant effects, but also deleterious effects on mRNA stability and translation. Thus, proper formulation of the mRNA is crucially important. Many approaches for RNA formulation have already been tested, with mixed success. In this review we discuss the state-of-the-art and future trends for mRNA-nanoparticle formulations for HIV vaccination, both in the prophylactic and in the therapeutic setting.

Poly(beta-amino ester)s as gene delivery vehicles: challenges and opportunities

INTRODUCTION

Gene delivery technologies are being developed for an increasing number of biomedical applications, with delivery vehicles including viruses and non-viral materials. Among biomaterials used for non-viral gene delivery, poly(beta-amino ester)s (PBAEs), a class of synthetic, biodegradable polymers, have risen as a leading gene delivery vehicle that has been used for multiple applications in vitro and in vivo.

AREAS COVERED

This review summarizes the key properties of PBAEs and their development, including a discussion of the advantages and disadvantages of PBAEs for gene delivery applications. The use of PBAEs to improve the properties of other drug delivery vehicles is also summarized.

EXPERT OPINION

PBAEs are designed to have multiple characteristics that are ideal for gene delivery, including their reversible positive charge, which promotes binding to nucleic acids as well as imparting high buffering capacity, and their rapid degradability under mild conditions. Simultaneously, some of their properties also lead to nanoparticle instability and low transfection efficiency in physiological environments. The ease with which PBAEs can be chemically modified as well as non-covalently blended with other materials, however, allows them to be customized specifically to overcome delivery barriers for varied applications.

mRNA Vaccine Era-Mechanisms, Drug Platform and Clinical Prospection

Messenger ribonucleic acid (mRNA)-based drugs, notably mRNA vaccines, have been widely proven as a promising treatment strategy in immune therapeutics. The extraordinary advantages associated with mRNA vaccines, including their high efficacy, a relatively low severity of side effects, and low attainment costs, have enabled them to become prevalent in pre-clinical and clinical trials against various infectious diseases and cancers. Recent technological advancements have alleviated some issues that hinder mRNA vaccine development, such as low efficiency that exist in both gene translation and in vivo deliveries. mRNA immunogenicity can also be greatly adjusted as a result of upgraded technologies. In this review, we have summarized details regarding the optimization of mRNA vaccines, and the underlying biological mechanisms of this form of vaccines. Applications of mRNA vaccines in some infectious diseases and cancers are introduced. It also includes our prospections for mRNA vaccine applications in diseases caused by bacterial pathogens, such as tuberculosis. At the same time, some suggestions for future mRNA vaccine development about storage methods, safety concerns, and personalized vaccine synthesis can be found in the context.

Surface-Functionalized PEGylated Nanoparticles Deliver Messenger RNA to Pulmonary Immune Cells

Nanoparticles designed as messenger RNA (mRNA) carriers to deliver gene medicine have shown great potential to change the way lung disease states are managed. Controlling their delivery to the lung and the transgene expression in a specific population of cells remains a challenge. Here, we developed a series of nanoparticles with polyethylene glycol (PEG) corona prepared by condensing mRNA with PEG-grafted-polyethyleneimine (PEI-g-PEG) with different PEG terminal functional groups and grafting ratios. PEGylated nanoparticles (PEG grafting ratio was 0.5%) with amino or amino acid terminal groups showed the highest transgene expression levels in the lung following systemic administration, and cell profiling analysis indicated that pulmonary immune cells contributed to the majority of expression. We also showed that these nanoparticles can be prepared by the flash nanocomplexation method, which is a scalable and reproducible process, yielding lyophilizable nanoparticles that were stable for at least 4 months at -20 °C. These results suggest that these surface-functionalized PEGylated nanoparticles may serve as desirable carriers to deliver mRNA to the lung for pulmonary immunomodulation.

The challenge and prospect of mRNA therapeutics landscape

Messenger RNA (mRNA)-based therapeutics hold the potential to cause a major revolution in the pharmaceutical industry because they can be used for precise and individualized therapy, and enable patients to produce therapeutic proteins in their own bodies without struggling with the comprehensive manufacturing issues associated with recombinant proteins. Compared with the current therapeutics, the production of mRNA is much cost-effective, faster and more flexible because it can be easily produced by in vitro transcription, and the process is independent of mRNA sequence. Moreover, mRNA vaccines allow people to develop personalized medications based on sequencing results and/or personalized conditions rapidly. Along with the great potential from bench to bedside, technical obstacles facing mRNA pharmaceuticals are also obvious. The stability, immunogenicity, translation efficiency, and delivery are all pivotal issues need to be addressed. In the recently published research results, these issues are gradually being overcome by state-of-the-art development technologies. In this review, we describe the structural properties and modification technologies of mRNA, summarize the latest advances in developing mRNA delivery systems, review the preclinical and clinical applications, and put forward our views on the prospect and challenges of developing mRNA into a new class of drug.

Topology-assisted, photo-strengthened DNA/siRNA delivery mediated by branched poly(β-amino ester)s via synchronized intracellular kinetics

Photo-degradable, branched poly(β-amino ester)s (BPAE-NB) were developed to mediate topology-assisted trans-membrane gene delivery as well as photo-strengthened intracellular gene release.

Fabrication Of Dual pH/redox-Responsive Lipid-Polymer Hybrid Nanoparticles For Anticancer Drug Delivery And Controlled Release

BACKGROUND

The development of biocompatible nanocarriers that can efficiently encapsulate and deliver anticancer drug to the tumor site and provide controlled release of cargos in response to the specific cues for cancer therapy is of great significance.

METHODS

In this work, dual pH/redox-responsive fabrication of hybrid lipid-polymer nanoparticles (LPNPs) self-assembled from amphiphilic polymer poly(ethylene glycol) methyl ether-grafted disulfide-poly(β-amino esters) (PBAE-ss-mPEG) and PEGylated lipid were prepared and used as drug delivery carriers. The optimization of PEGylated lipid modification was confirmed by analysis of particle size, polydispersity index (PDI), cellular uptake, serum stability, and drug loading capacity. The pK b value of LPNPs was determined as 6.55, indicating the pH-sensitivity. The critical micelle concentration (CMC) values and zeta-potential of LPNPs at different pH values were investigated to confirm its pH-sensitivity. The morphology of LPNPs before and after incubation with reducing agent was imaged to study the redox-responsibility.

RESULTS

The in vitro results showed that the drug had controlled release from LPNPs triggered by low pH and high concentration of reducing agent. Furthermore, the cytotoxicity of LPNPs was very low, and the doxorubicin (DOX)-loaded LPNPs could efficiently induce the death of tumor cells in comparison to free DOX.

CONCLUSION

All results demonstrated that the fabricated LPNPs could be potential anticancer drug delivery carriers with a pH/redox-triggered drug release profile, and PEGylated lipid modification might be a useful method to fabricate the drug delivery platform.

Recent advances in polymeric materials for the delivery of RNA therapeutics

Introduction: The delivery of nucleic acid therapeutics through non-viral carriers face multiple biological barriers that reduce their therapeutic efficiency. Despite great progress, there remains a significant technological gap that continues to limit clinical translation of these nanocarriers. A number of polymeric materials are being exploited to efficiently deliver nucleic acids and achieve therapeutic effects. Areas covered: We discuss the recent advances in the polymeric materials for the delivery of nucleic acid therapeutics. We examine the use of common polymer architectures and highlight the challenges that exist for their development from bench side to clinic. We also provide an overview of the most notable improvements made to circumvent such challenges, including structural modification and stimuli-responsive approaches, for safe and effective nucleic acid delivery. Expert opinion: It has become apparent that a universal carrier that follows 'one-size' fits all model cannot be expected for delivery of all nucleic acid therapeutics. Carriers need to be designed to exhibit sensitivity and specificity toward individual targets diseases/indications, and relevant subcellular compartments, each of which possess their own unique challenges. The ability to devise synthetic methods that control the molecular architecture enables the future development that allow for the construction of 'intelligent' designs.

Codelivery of mRNA with α-Galactosylceramide Using a New Lipopolyplex Formulation Induces a Strong Antitumor Response upon Intravenous Administration

Recently, the use of mRNA-based vaccines for cancer immunotherapy has gained growing attention. Several studies have shown that mRNA delivered in a vectorized format can generate a robust and efficient immune response. In this work, a new lipopolyplex vector (multi-LP), incorporating the immune adjuvant α-galactosylceramide (α-GalCer) and a multivalent cationic lipid, was proposed for the in vivo delivery of mRNA into antigen-presenting cells. We demonstrate that dendritic cells (DCs) can be targeted in vivo by intravenous administration of a α-GalCer-/mRNA-loaded multi-LP vector, without the need for its functionalization with cell-specific antibodies or ligands. The multi-LP nanoparticles loaded with a reporter mRNA efficiently led to high expression of the enhanced green fluorescence protein in DCs both in vitro and in vivo, exhibiting an intrinsic selectivity for DCs. Finally, the TRP2-mRNA/α-GalCer-based multi-LP vaccine induced a significant therapeutic effect against a highly malignant B16-F10 melanoma tumor. This study provides the first evidence that a combination of antigen-mRNA and α-GalCer can be used as an effective antitumor vaccine, inducing strong innate and adaptive immune responses.

Delivering the Messenger: Advances in Technologies for Therapeutic mRNA Delivery

mRNA has broad potential as a therapeutic. Current clinical efforts are focused on vaccination, protein replacement therapies, and treatment of genetic diseases. The clinical translation of mRNA therapeutics has been made possible through advances in the design of mRNA manufacturing and intracellular delivery methods. However, broad application of mRNA is still limited by the need for improved delivery systems. In this review, we discuss the challenges for clinical translation of mRNA-based therapeutics, with an emphasis on recent advances in biomaterials and delivery strategies, and we present an overview of the applications of mRNA-based delivery for protein therapy, gene editing, and vaccination.

pH-Sensitive Polymers as Dynamic Mediators of Barriers to Nucleic Acid Delivery

The nonviral delivery of exogenous nucleic acids (NA) into cells for therapeutic purposes has rapidly matured into tangible clinical impact. Synthetic polymers are particularly attractive vectors for NA delivery due to their relatively inexpensive production compared to viral alternatives and their highly tailorable chemical properties; indeed, many preclinical investigations have revealed the primary biological barriers to nonviral NA delivery by systematically varying polymeric material properties. This review focuses on applications of pH-sensitive chemistries that enable polymeric vectors to serially address multiple biological barriers to NA delivery. In particular, we focus on recent innovations with in vivo evaluation that dynamically enable colloidal stability, cellular uptake, endosomal escape, and nucleic acid release. We conclude with a summary of successes to date and projected areas for impactful future research.

Ionizable Amino-Polyesters Synthesized via Ring Opening Polymerization of Tertiary Amino-Alcohols for Tissue Selective mRNA Delivery

The utility of messenger RNA (mRNA) as a therapy is gaining a broad interest due to its potential for addressing a wide range of diseases, while effective delivery of mRNA molecules to various tissues still poses a challenge. This study reports on the design and characterization of new ionizable amino-polyesters (APEs), synthesized via ring opening polymerization (ROP) of lactones with tertiary amino-alcohols that enable tissue and cell type selective delivery of mRNA. With a diverse library of APEs formulated into lipid nanoparticles (LNP), structure-activity parameters crucial for efficient transfection are established and APE-LNPs are identified that can preferentially home to and elicit effective mRNA expression with low in vivo toxicity in lung endothelium, liver hepatocytes, and splenic antigen presenting cells, including APE-LNP demonstrating nearly tenfold more potent systemic mRNA delivery to the lungs than vivo-jetPEI. Adopting tertiary amino-alcohols to initiate ROP of lactones allows to control polymer molecular weight and obtain amino-polyesters with narrow molecular weight distribution, exhibiting batch-to-batch consistency. All of which highlight the potential for clinical translation of APEs for systemic mRNA delivery and demonstrate the importance of employing controlled polymerization in the design of new polymeric nanomaterials to improve in vivo nucleic acid delivery.